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Date: Wed, 13 Dec 2006 16:01:22 +0100
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: Trond Myklebust <trond.myklebust@....uio.no>
Cc: Andrew Morton <akpm@...l.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: [PATCH] nfs: fix NR_FILE_DIRTY underflow
On Wed, 2006-12-13 at 07:26 -0500, Trond Myklebust wrote:
> On Wed, 2006-12-13 at 13:12 +0100, Peter Zijlstra wrote:
> > Still testing this patch, but it looks good so far.
> >
> > ---
> > Just setting PG_dirty can cause NR_FILE_DIRTY to underflow
> > which is bad (TM).
> >
> > Use set_page_dirty() which will do the right thing.
>
> Actually, I'd prefer to have it do the right thing by getting rid of
> that call to test_clear_page_dirty() inside
> invalidate_inode_pages2_range(). That is causing loss of data integrity,
> and is what is causing us to have to hack NFS in the first place.
Ah, I think I see what your problem is there.
How about this totally untested patch:
---
Delay clearing the dirty page state till after removing it from the
mapping in invalidate_inode_pages2_range(). This will give
try_to_release_pages() a shot to flush dirty data.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
fs/nfs/file.c | 2 --
include/linux/page-flags.h | 2 ++
mm/page-writeback.c | 17 +++++++++++------
mm/truncate.c | 11 +++--------
4 files changed, 16 insertions(+), 16 deletions(-)
Index: linux-2.6-git/fs/nfs/file.c
===================================================================
--- linux-2.6-git.orig/fs/nfs/file.c 2006-12-13 15:31:26.000000000 +0100
+++ linux-2.6-git/fs/nfs/file.c 2006-12-13 15:39:33.000000000 +0100
@@ -320,8 +320,6 @@ static int nfs_release_page(struct page
*/
if (!(gfp & __GFP_FS))
return 0;
- /* Hack... Force nfs_wb_page() to write out the page */
- SetPageDirty(page);
return !nfs_wb_page(page_file_mapping(page)->host, page);
}
Index: linux-2.6-git/include/linux/page-flags.h
===================================================================
--- linux-2.6-git.orig/include/linux/page-flags.h 2006-12-13 15:35:50.000000000 +0100
+++ linux-2.6-git/include/linux/page-flags.h 2006-12-13 15:36:14.000000000 +0100
@@ -252,7 +252,9 @@ static inline void SetPageUptodate(struc
#define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)
struct page; /* forward declaration */
+struct address_space;
+int __test_clear_page_dirty(struct address_space *mapping, struct page *page);
int test_clear_page_dirty(struct page *page);
int test_clear_page_writeback(struct page *page);
int test_set_page_writeback(struct page *page);
Index: linux-2.6-git/mm/page-writeback.c
===================================================================
--- linux-2.6-git.orig/mm/page-writeback.c 2006-12-13 15:34:15.000000000 +0100
+++ linux-2.6-git/mm/page-writeback.c 2006-12-13 15:39:41.000000000 +0100
@@ -850,13 +850,8 @@ int set_page_dirty_lock(struct page *pag
}
EXPORT_SYMBOL(set_page_dirty_lock);
-/*
- * Clear a page's dirty flag, while caring for dirty memory accounting.
- * Returns true if the page was previously dirty.
- */
-int test_clear_page_dirty(struct page *page)
+int __test_clear_page_dirty(struct address_space *mapping, struct page *page)
{
- struct address_space *mapping = page_mapping(page);
unsigned long flags;
if (!mapping)
@@ -880,6 +875,16 @@ int test_clear_page_dirty(struct page *p
write_unlock_irqrestore(&mapping->tree_lock, flags);
return 0;
}
+
+/*
+ * Clear a page's dirty flag, while caring for dirty memory accounting.
+ * Returns true if the page was previously dirty.
+ */
+int test_clear_page_dirty(struct page *page)
+{
+ struct address_space *mapping = page_mapping(page);
+ return __test_clear_page_dirty(mapping, page);
+}
EXPORT_SYMBOL(test_clear_page_dirty);
/*
Index: linux-2.6-git/mm/truncate.c
===================================================================
--- linux-2.6-git.orig/mm/truncate.c 2006-12-13 15:36:38.000000000 +0100
+++ linux-2.6-git/mm/truncate.c 2006-12-13 15:44:01.000000000 +0100
@@ -307,18 +307,12 @@ invalidate_complete_page2(struct address
return 0;
write_lock_irq(&mapping->tree_lock);
- if (PageDirty(page))
- goto failed;
-
BUG_ON(PagePrivate(page));
__remove_from_page_cache(page);
write_unlock_irq(&mapping->tree_lock);
ClearPageUptodate(page);
page_cache_release(page); /* pagecache ref */
return 1;
-failed:
- write_unlock_irq(&mapping->tree_lock);
- return 0;
}
/**
@@ -386,12 +380,13 @@ int invalidate_inode_pages2_range(struct
PAGE_CACHE_SIZE, 0);
}
}
- was_dirty = test_clear_page_dirty(page);
+ was_dirty = PageDirty(page);
if (!invalidate_complete_page2(mapping, page)) {
if (was_dirty)
set_page_dirty(page);
ret = -EIO;
- }
+ } else
+ __test_clear_page_dirty(mapping, page);
unlock_page(page);
}
pagevec_release(&pvec);
-
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